# [OS X TeX] Is There A Reason...

Herbert Schulz herbs at wideopenwest.com
Mon Apr 26 14:17:03 CEST 2010

On Apr 26, 2010, at 2:21 AM, Louis Talman wrote:

> Is there a good reason why \chapter, \section, and \subsection don't handle the $$and$$ delimiters properly, but do handle $...$ right?  Or is it a bug?  The following minimal example is from a book a colleague is writing, and we both wonder.
>
> The example appears to compile correctly, and even displays a page in TeXShop.  But a second compile fails, and there's a mess in the .toc file that seems to cause the failure.  The mess is put there by the first compile.  What's going on?
>
> ------------Cut here----------------
>
> \documentclass{book}
>
> \begin{document}
>
> \tableofcontents
>
> \chapter{$2 \times 2$ }
>
> \chapter{$$3 \times 3$$ }
>
> \end{document}
>
> ------------Cut here----------------
>
>
> --Lou Talman
>  Department of Mathematical & Computer Sciences
>  Metropolitan State College of Denver

Howdy,

Since the contents of \chapter, etc., must be saved and expanded again anything that goes into the command must be robust, i.e., protected against premature expansion. Unfortunately the $$and$$ are not, by default, robust macros in LaTeX2e by default. You can fix this by using the fixltx2e package,

\usepackage{fixltx2e}